Getting into CRT Shaders as a newcomer can be initially overwhelming, so here is some advice I have on how to get started.
There isn’t really a specific CRT shader to use for a certain kind of display. This is because CRT Shaders are more geared towards achieving a certain aesthetic and look as opposed to being built for use on a certain display. There isn’t a specific shader that I would say to avoid, but for the time being, I would stay away from CRT-Royale. This isn’t because it is a bad shader or that you shouldn’t use it, but because it’s a very, very complex shader and has a huge amount of parameters involved, so being a newcomer you will be easily overwhelmed by it. It is for those who want to get very technical with the little bits and details of CRT emulation.
I do recommend leaving integer scaling ON. This is because CRT shaders are aimed at emulating the individual scanlines on a CRT display that are drawn when the image is rendered. Without integer scaling, you can run into issues where you see visible artifacts on screen that are a result of uneven scanlines due to non-integer based resolutions. This is why when you see screenshots of these shaders online, you can see ripple patterns and other artifacts when you are not viewing them in full-screen or viewing the image at its full size.
An integer-based resolution is one that is a multiple of the said horizontal and vertical resolution. For example, PS1 games in Retroarch are emulated and displayed with a 240-pixel vertical height. Therefore a 2x integer of 240 is 480, a 3x integer of 240 is 720, a 4x integer of 240 is 960, and so forth.
Unfortunately, this will shrink or expand the size of the screen in Retroarch, depending on if you want to have overscan and want to cut out the outsides of the image to fit the whole screen, or you will have pillar boxing on all sides if you want to see all of the content being displayed.
With your 1440p monitor, even with integer scaling turned on, you can mitigate the amount of pillar boxing excessively since 240 is a 6x integer of 1440. You can leave integer scaling turned on and set the aspect ratio to 4:3 so you can have the proper aspect ratio and games won’t look stretched. However, some consoles such as the Sega Genesis and the SNES use a vertical resolution of 224 pixels, which means that it isn’t a complete integer of 1440, and therefore with integer scaling, you will have some pillar boxing on the top and bottom. It isn’t too severe, however.
With your Galaxy Note 20, on the other hand, and its 1080p vertical resolution, you, unfortunately, will have pillar boxing on all sides because 1080 isn’t an integer of 240 or 224. You can find this out with any resolution by taking the vertical resolution of the display and diving it by the vertical resolution of the console you are emulating (for example, 1440/240=6 which makes it a 6x integer. However, 1080/240=4.5, which isn’t an integer multiple and therefore will result in uneven scanlines without integer scaling).
If you do want to run without integer scaling, you can try CRT-Easymode and CRT-Lottes as they tend to be CRT shaders that tend to look the best with non-integer resolutions. CRT-Aperture, on the other hand, looks absolutely atrocious at non-integer based resolutions and must be run with integer scaling enabled.
There are different versions of CRT shaders made by various users that aim to accomplish different things. For example, shaders marked with “Halation” or “Glow” are made to emulate the CRT Phosphor glow of the display, and often appeal to people who like the “glow” of CRT displays. Others have very specific applications. For example, CRT-Royale-NTSC-Composite is a preset of CRT-Royale configured to emulate the look of a CRT display with a composite signal, same with CRT-Royale-NTSC-S-Video (which emulates S-Video signals). It would take me quite a long time, and it would be quite the long read to this already long response to go through every single one, so I would advise doing intensive research on the various versions of the shaders, or perhaps just testing them out and noting the differences between them.
I don’t know personally how the process for shaders being updated through Retroarch’s online updater works, so if you want to stay updated with the latest versions of these shaders being released, I would suggest using the links provided by the users and download them from there.
As a newcomer, I would say just experiment with different shaders. I find that learning more about the technical aspects of how CRT displays work actually helps me in learning how to better configure these shaders to work as I want them. CRT-Easymode, CRT-Lottes, CRT-Hyllian, and CRT-Geom are great CRT shaders to start with and mess around. They don’t have too many parameters to overwhelm you and are great for getting your feet wet. It all comes down to personal preference in the end though, and what kind of look you are after specifically.
I personally have been using CRT-Guest-Dr-Venom 2, as I find that it is the best shader for running games that run at 480i (interlaced mode games such as Tekken 3). I also has a lot of parameters for fine-tuning colors, adjusting scanline sizes and CRT mask intensity, and many other parameters. Here is a screenshot of the look I have achieved with that shader and my current configuration in Gran Turismo.
Of course, feel free to browse and experiment with what you find most appealing. There are lots of different things you can do and I’d say just start trying different shaders out, tweak various parameters, and see where you can go with it. I know this is a very long read, but hopefuly it will help you out in some way or another 
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Then I got to learning more about this stuff and all the possibilities and was hooked 
